ALBERT

Description: Abstract 4815 Algae preparations are commonly used in complementary and alternative medicine for presumed anti-oxidant, anti-inflammatory, and anti-cancer properties. In this study, we have examined the effects of extracts from algae and algae components on the proliferation of normal hematopoietic and leukemia cells. To prepare extracts, 1 gram of Dunaliella salina (Dun), Astaxanthin (Ast), Spirulina (C-phycocyanin) (Spir), or Aphanizomenon flos-aquae (AFA) were added to 10 ml of 70% ethanol and incubated at 4°C on a shaker for 24 hours. The slurry was centrifuged at 400 g for 10 minutes at 4°C, and the supernatant was filtered through 413-grade filter paper. Leukemia cell lines were purchased from ATCC and blood or marrow aspirates from normal subjects or patients with leukemia were subjected to Ficoll-Hypaque density gradient centrifugation. CD34+ cells were isolated using Miltenyi Biotec MiniMACS magnetic bead cell separation columns. To determine effects on cell proliferation, increasing concentrations of algae extracts were added in fresh medium to plated cells, and MTT reagent was added followed by detergent and absorbance readings were recorded at 570 nm. Leukemic cell lines such as HL60 and MV4-11 were significantly inhibited by Ast and AFA at concentration of 0.8 mg/mL of extract (p

Description: Proteasome inhibitors block degradation of the NF-κB regulator, IκB, resulting in inhibition of NF-κB nuclear localization. Proteasome inhibitors have been tested in the setting of refractory acute leukemia, with proteasome inhibition demonstrated within leukemic blasts. Arsenic trioxide (AsO3) has also been shown to inhibit NF-κB in leukemia. Since NF-κB is constitutively activated in primitive AML cells and serves as a regulator of many genes which encode proliferative and survival responses, we have begun to explore the effects of AsO3 and bortezomib (PS-341, VelcadeTM ), on AML cell lines and primary cells. The farnesyl transferase inhibitors (FTIs) also inhibit AML proliferation, and their effects in combination with bortezomib have also been explored. Because FTIs may inhibit signal transduction pathways independent of those affected by NF-κB inhibition, and because FTIs may indirectly inhibit NF-κB function via Akt inhibition, the effects of combining these agents with other NF-κB agents on AML cells in vitro have also been explored. Bortezomib, at concentrations of 4nM or greater, inhibited NF-κB in AML cell lines and primary cells as did AsO3 at concentrations of 1 nM or greater. NF-kappa B was measured by ELISA for p65 NF-κB activity. The nonpeptidomimetic FTI, R115777 (J&J), did not inhibit NF-κB at concentrations up to 100 nM, concentrations which effectively inhibit farnesylation of target proteins, whereas the FTI, L-744832 (Merck), was able to inhibit NF-κB expression at 1 μM from 24 to 72 hours of exposure. In the HL60 cell line, inhibited by FTI and bortezomib independently, the combination did not appear to have additive or synergistic effects. Furthermore, the effects of combined exposure to FTI and bortezomib on expression of activated caspase 3 or activated PARP cleavage were no greater than with bortezomib alone. Likewise, combination effects on expression of phosphorylated AKT or ERK were not observed. In contrast, the combination of bortezomib and AsO3 resulted in decreased phospho-ERK expression and increased expression of cleaved PARP, suggesting increased apoptosis. When cytarabine, 100 nM was combined with bortezomib at 1 to 4 nM, no effect on timing of administration was noted, and apoptosis was increased with the combination as evidenced by an increase in cleaved PARP expression. Greater inhibition of proliferation was seen with this combination than with individual agents as demonstrated in MTT assays with combination index calculations suggesting synergism. With this combination, co-culture with an endothelial monolayer did not prevent the increased apoptosis noted with combined cytarabine and bortezomib. These studies suggest that future studies combining proteasome inhibition with standard chemotherapeutic agents or with other inhibitors of NF-κB like Arsenic trioxide may have greater antileukemic activity by inducing apoptosis in AML cells in vivo as well as in vitro, without obvious limitations of other targeted agents and drugs that are extruded by multridrug resistance transporters.

Description: Stromal cell derived factor-1 (SDF-1α) and its receptor, CXCR4 play a role in the trafficking of CD34+ cells. AMD3100, a selective CXCR4 antagonist, can mobilize hematopoietic progenitors from marrow to peripheral blood in healthy human volunteers and in patients with multiple myeloma and non-Hodgkin’s lymphoma (Flomenberg et al, Blood 102, 39a, 2003). Overexpression of CXCR4 on human CD34+ progenitors increases their proliferation and NOD/SCID repopulating capacity (Kahn et al. Blood 103:2942, 2004). Since CXCR4 has been found to regulate the migration and development of AML stem cells in NOD/SCID mice, we studied the effect of AMD3100 on AML cells from the standpoint of proliferation and in vitro transendothelial transmigration utilizing a transwell system. AMD3100 (from AnorMED, Inc.), at concentrations from 0.1 to 1.0 ng/ml did not affect the viability or porliferation of purified AML blasts (n=4). AMD3100 did not influence the adherence of AML blasts to endothelial monolayers. In the presence of 0.1 to 1 ng/ml AMD-3100, the transmigration of normal CD34+ cells stimulated by 100 ng/ml SDF-1α through a human umbilical vein endothelial cell (HUVEC) monolayer was completely inhibited. Likewise, the transmigration of AML blasts through HUVECs was not altered by AMD3100 exposure, but the SDF-1α mediated transmigration was inhibited by AMD3100 from 0.1 to 1 ng/ml. The same effect was noted with AML transmigration through marrow stromal layers. The increase in transmigration through endothelial cells stimulated with G-CSF was not inhibited by AMD3100 whereas the transmigration stimulated by interleukin-8 was inhibited. When AMD3100 was placed in the bottom of the migration chamber, no independent effects on AML transmigration were noted. Co-culture of AML blasts with stromal monolayers protected blasts from apoptosis. This protection was not altered by SDF-1α, AMD3100, nor by the combination. These in vitro results demonstrate that AMD3100 can influence the migratory capacity of AML cells but has no direct effects on their proliferation or survival. Further in vitro and in vivo studies will be required to elucidate the role that this unique chemokine antagonist has in the mobilization potential of AML blasts or progenitors or in the interactions of AML cells with their microenvironment. Such studies have implications for AML autografting and AML blast interactions with extramedullary endothelial cells.

Description: Abstract 3549 Introduction: Decitabine (5-aza-2'-deoxyctiidine) has demonstrated single agent activity in newly diagnosed acute myelogenous leukemia (AML). Complete response rates are low, however, and this agent has not been extensively studied in settings of relapsed or refractory disease where treatment responses are generally short in the absence of allogeneic stem cell transplantation. Most AML cases have activation of the mTOR pathway as evidenced by expression of phosphorylated p70S6 kinase or phopho-4EBP1. Since inhibitors of the mTOR pathway such as the tuberous sclerosis genes (TSC1 and TSC2) are hypermethylated in some cases of AML and there is evidence that decitabine may inhibit the PI3K/Akt pathway often activated after mTOR inhibition, we conducted a phase I study utilizing decitabine (DAC) followed by the mTOR inhibitor rapamycin in patients with relapsed/refractory AML to assess safety and feasibility. Methods: Patients ≥ 18 years of age with non-M3 AML with relapsed or refractory disease were eligible for this protocol. Patients who had relapsed after allogeneic stem cell transplant were eligible if they did not have active graft vs. host disease 〉grade 1 of skin. Patients received DAC 20 mg/m2 intravenously daily for 5 days followed by rapamycin from day 6 to 25 at doses of 2mg, 4mg, and 6 mg/day in a 3+3 dose escalation design. Cycles were 28 days in duration, and in the absence of overt progression of disease, patients could receive up to 6 cycles of therapy. A marrow aspirate was performed at day 5 to assess effects of single agent decitabine on mTOR and Akt pathway mediators. Bone marrow responses were assessed after cycles 1 and 3. Results: Thirteen patients were treated, and 12 are available for safety evaluation. The median age of patients is 64 years (range 46–78). Median marrow blast percentage at enrollment was 35% (range 6–83%). In the 2 mg dose cohort, 1 patient had disease progression before completion of cycle 1 and another patient in the first cohort had a history of prolonged neutropenia at the time of enrollment and experienced reversible grade 3 mucositis, which was deemed a DLT. Three more patients enrolled at this dose, and no further DLTs were observed, allowing dose escalation to the 4 mg and 6 mg cohorts. The MTD has not yet been reached. Reversible grade 2–3 mucositis occurred in 7 patients, but no other recurrent non-hematologic toxicities were seen. On the 2 mg cohort, all patients achieved therapeutic rapamycin levels (5–15 ng/ml) during the first cycle, and in 5/7 patients, the therapeutic level was achieved within 4 days of beginning rapamycin. In the 2 mg cohort, no cumulative increase in rapamycin levels occurred over subsequent cycles (4/7 completed 〉1 cycle). In the 4 mg cohort, one patient had an elevated level at day 9, and one patient on concomitant voriconazole had supra-therapeutic levels at day 16 and day 23. At the end of one cycle, 4 patients demonstrated disease progression, 5 had stable marrow blasts, and 4 demonstrated a decline in marrow blast percentage. Median survival to date is 6 months (range 1 to 15+ months). Two patients proceeded to allogeneic stem cell transplant, and one patient who relapsed shortly after stem cell transplant survived 4 months and demonstrated stable donor chimerism during that time. As assessed by Western blotting in 9 patients with evaluable samples at baseline, 87% of these cases expressed phospho (p)-4EBP1 at diagnosis, 56% p70S6K, 67% peIF4E, and 44% pAKT. In the 7 patients with Western blot samples evaluable at the end of cycle 1, 3 had decreases in p4EBP1 after the first cycle, and 4 had increased expression. Of the 7 evaluable patients, only 3 expressed baseline p70S6K, and this decreased in 2 and was unchanged in 1 patient. Conclusion: The combination of decitabine and rapamycin can be safely administered to patients with relapsed/refractory AML. Based on this phase I data, a phase II cohort to define efficacy can be conducted at the 2 mg rapamycin dosing given the therapeutic rapamycin levels demonstrated at this dose. Effects on mTOR mediators and on AKT can be serially assessed and are variable. Correlation with clinical response will require a phase II study. This trial is registered at clinical trials.gov as NCT00861874. Disclosures: Liesveld: Eisai: Research Funding, Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Ariad: Honoraria. Off Label Use: This is a phase 1 study to see if rapamycin is safe in AML.